Polyolefin Compositions

ABSTRACT

Polyolefin compositions particularly suitable for cast film, exhibiting heat sealability, retortability, low haze and stiffness, comprising:
     1) 75-85% of a propylene homopolymer or copolymer of propylene with ethylene and/or one or more C 4 -C 10  α-olefin(s), the homopolymer or copolymer having melting temperature equal to or higher than 150° C.,   2) 15-25% of a copolymer of ethylene with one or more C 4 -C 10  α-olefin(s) containing from 20 to 30% of said C 4 -C 10  α-olefin(s);
 
said composition having MFR (at 230° C., 2.16 kg) of from 5-10 g/10 min, the total content of ethylene of from 10 to 20%, the total content of C 4 -C 10  α-olefin(s) of from 2 to 8%, the ratio XStot/XSm of the total fraction soluble in Xylene at room temperature to the fraction soluble in Xylene at room temperature of the matrix component (1) of from 5 to 15, and the value of the intrinsic viscosity of the total fraction soluble in Xylene at room temperature (XSIVtot) of 1.5 dl/g or less.

This application is the U.S. national phase of International ApplicationPCT/EP2010/058916, filed Jun. 23, 2010, claiming priority to EuropeanApplication 09163842.9 filed Jun. 26, 2009 and the benefit under 35U.S.C. 119(e) of U.S. Provisional Application No. 61/269,634, filed Jun.26, 2009; the disclosures of International ApplicationPCT/EP2010/058916, European Application 09163842.9 and U.S. ProvisionalApplication No. 61/269,634, each as filed, are incorporated herein byreference.

The present invention concerns polyolefin compositions comprising apropylene polymer component selected from propylene homopolymers andpropylene random copolymers containing ethylene and/or other α-olefinsas comonomers, and a copolymer of ethylene with C₄-C₁₀ α-olefins.

The compositions of the present invention can be easily converted intovarious kinds of finished or semi-finished articles. In particular, thecompositions of the present invention are suitable for filmapplications, particularly for cast films, exhibiting heat seal-ability,retortability and good optical properties (low haze on film) togetherwith high flexural modulus (stiffness). The compositions can be used inparticular for those film applications requiring good optical propertiesand stiffness such as packaging for fresh vegetables, laminatedretortable and flexible packaging and clear retortable pouches. Thecompositions are also suitable for injection moulding applications suchas batteries and caps and closures. Compositions comprising crystallinepolypropylene matrix and a rubbery phase formed by an elastomericcopolymer of ethylene with α-olefins are already known in the art, anddescribed in particular in European patents 170 255, 373 660, 603723,and 1135440 and in the International Application WO 2008/061843.

Said compositions exhibit impact resistance and, in the case of Europeanpatent 373 660, 603723, 1135440, transparency values interesting formany applications. However the overall balance of properties is stillnot totally satisfactory in the whole range of possible applications, inview of the high standards required by the market.

Therefore, there still remains a continuous demand for compositions ofthis kind with improved properties balanced for specific targetapplications.

An excellent balance of properties particularly in view of applicationfor films and retortable packaging has now been achieved by thepolyolefin compositions of the present invention comprising, in percentby weight referred to the sum of component 1) and 2):

-   -   1) 75-85% of a propylene homopolymer or copolymer of propylene        with ethylene and/or one or more C₄-C₁₀ α-olefin(s), the said        homopolymer or copolymer having melting temperature (Tm-DSC)        equal to or higher than 150° C. preferably higher than 154° C.    -   2) 15-25% of a copolymer of ethylene with one or more C₄-C₁₀        α-olefin(s) containing from 20 to 30 wt %, preferably from 22 to        28 wt % of said C₄-C₁₀ α-olefin(s); said composition having    -   the value of melt flow rate (MFR) at 230° C., 2.16 kg of from 5        to10, preferably of from 6 to 8 g/10 min.    -   the total content of ethylene of from 10 to 20, preferably from        12 to 18 wt %,    -   the total content of C₄-C₁₀ α-olefin(s) of from 2 to 8,        preferably from 3 to 7 wt %, more preferably of from 5 to 7    -   the ratio (XStot/XSm) of the total fraction soluble in Xylene at        room temperature to the fraction soluble in Xylene at room        temperature of the component (1) (matrix) of from 5 to 15,        preferably of from 8 to 12, and    -   the value of the intrinsic viscosity of the total fraction        soluble in Xylene at room temperature (XSIVtot) is of 1.5 dl/g        or less, preferably of 1.3 or less, more preferably of from 1.1        to 1.3 dl/g;

Particularly preferred features for the compositions of the presentinvention are:

-   -   the fraction soluble in Xylene at room temperature of        component (1) (XSm) equal to or less than 2 wt %.    -   when the matrix component (1) is a copolymer of propylene, the        amount of units derived from ethylene and/or one or more C₄-C₁₀        α-olefin(s) is less than 1.5 wt %, preferably less than 1 wt %        of the component (1), more preferably less than 0.5 wt %        (minirandom copolymer).    -   the MFR (at 230° C., 2.16 Kg) of component (1) is from 5 to 10        g/10 min, preferably of from 6 to 8 g/10 min.    -   the total fraction soluble in Xylene at room temperature (XStot)        of less than 20 wt % or less, preferably of 18 wt % or less,        more preferably of from 10 to 18 wt %    -   the flexural modulus of more than 900 MPa, more preferably more        than 1000 MPa;    -   the ratio of the total content of ethylene to the total content        of C₄-C₁₀ α-olefin(s) of 2.3 or more.

Throughout the present Specification the term “copolymer” is meant toinclude also polymers containing, in addition to the main monomer, morethan one kind of further comonomers. XStot is the total fraction solublein Xylene at room temperature in percent by weight with respect to thesum of the matrix component (1) and the rubber component (2). XSm is thefraction soluble in Xylene at room temperature of component (1) inpercent by weight referred to the component (1). Tm-DSC is the meltingtemperature of the matrix component (1) as measured on the composition,according to the method reported below, before the addition ofnucleating agents that can raise the melting temperature. Thus, thefinal melting temperature measured on the composition after the additionof a nucleating agent can be higher (e.g. 3 to 5° C. higher). Nucleatingagents can be required for some specific end-use (e.g. injectionmoulding application).

The compositions of the present invention provide in particular acombination of high flexural modulus, good film quality (low fish eyesnumber) and excellent transparency on films (low haze).

The said C₄-C₁₀ α-olefins, which are or may be present as comonomers inthe components and fractions of the compositions of the presentinvention, are represented by the formula CH₂═CHR, wherein R is an alkylradical, linear or branched, with 2-8 carbon atoms or an aryl (inparticular phenyl) radical.

Examples of said C₄-C₁₀ α-olefins are 1-butene, 1-pentene, 1-hexene,4-methyl-1-pentene and 1-octene. Particularly preferred is 1-butene inthe rubber component (2) and ethylene in the matrix component (1).

The compositions of the present invention can be prepared by asequential polymerization, comprising at least two sequential steps,wherein components 1) and 2) are prepared in separate subsequent steps,operating in each step, except the first step, in the presence of thepolymer formed and the catalyst used in the preceding step. The catalystis added preferably only in the first step; however its activity is suchthat it is still active for all the subsequent steps.

Preferably component 1) is prepared before component 2).

Therefore, the present invention is further directed to a process forthe preparation of the polyolefin compositions as reported above, saidprocess comprising at least two sequential polymerization stages witheach subsequent polymerization being conducted in the presence of thepolymeric material formed in the immediately preceding polymerizationreaction, wherein the polymerization stage of propylene to the polymercomponent 1) is carried out in at least one stage, then at least onecopolymerization stage of mixtures of ethylene with one or more C₄-C₁₀α-olefin(s) to the elastomeric polymer component 2) is carried out. Thepolymerisation stages may be carried out in the presence of astereospecific Ziegler-Natta catalyst.

According to a preferred embodiment, all the polymerisation stages arecarried out in the presence of a catalyst comprising a trialkylaluminiumcompound, optionally an electron donor, and a solid catalyst componentcomprising a halide or halogen-alcoholate of Ti and an electron-donorcompound supported on anhydrous magnesium chloride. Catalysts having theabove-mentioned characteristics are well known in the patent literature;particularly advantageous are the catalysts described in U.S. Pat. No.4,399,054 and EP-A-45 977. Other examples can be found in U.S. Pat. No.4,472,524.

Preferably the polymerisation catalyst is a Ziegler-Natta catalystcomprising a solid catalyst component comprising:

a) Mg, Ti and halogen and an electron donor (internal donor),

b) an alkylaluminum compound and, optionally (but preferably),

c) one or more electron-donor compounds (external donor).

The internal donor is preferably selected from the esters of mono ordicarboxylic organic acids such as benzoates, malonates, phthalates andcertain succinates. They are described in U.S. Pat. No. 4,522,930,European patent 45977 and international patent applications WO 00/63261and WO 01/57099, for example. Particularly suited are the phthalic acidesters and succinate acids esters. Alkylphthalates are preferred, suchas diisobutyl, dioctyl and diphenyl phthalate and benzyl-butylphthalate.

Among succinates, they are preferably selected from succinates offormula (I) below:

wherein the radicals R₁ and R₂, equal to, or different from, each otherare a C₁-C₂₀ linear or branched alkyl, alkenyl, cycloalkyl, aryl,arylalkyl or alkylaryl group, optionally containing heteroatoms; theradicals R₃ to R₆ equal to, or different from, each other, are hydrogenor a C₁-C₂₀ linear or branched alkyl, alkenyl, cycloalkyl, aryl,arylalkyl or alkylaryl group, optionally containing heteroatoms, and theradicals R₃ to R₆ which are joined to the same carbon atom can be linkedtogether to form a cycle; with the proviso that when R₃ to R₅ arecontemporaneously hydrogen, R₆ is a radical selected from primarybranched, secondary or tertiary alkyl groups, cycloalkyl, aryl,arylalkyl or alkylaryl groups having from 3 to 20 carbon atoms;

or of formula (II) below:

wherein the radicals R₁ and R₂, equal to or different from each other,are a C₁-C₂₀ linear or branched alkyl, alkenyl, cycloalkyl, aryl,arylalkyl or alkylaryl group, optionally containing heteroatoms and theradical R₃ is a linear alkyl group having at least four carbon atomsoptionally containing heteroatoms.

The Al-alkyl compounds used as co-catalysts comprise Al-trialkyls, suchas Al-triethyl, Al-triisobutyl, Al-tri-n-butyl, and linear or cyclicAl-alkyl compounds containing two or more Al atoms bonded to each otherby way of O or N atoms, or SO₄ or SO₃ groups. The Al-alkyl compound isgenerally used in such a quantity that the Al/Ti ratio be from 1 to1000.

The external donor (c) can be of the same type or it can be differentfrom the succinates of formula (I) or (II). Suitable externalelectron-donor compounds include silicon compounds, ethers, esters suchas phthalates, benzoates, succinates also having a different structurefrom those of formula (I) or (II), amines, heterocyclic compounds andparticularly 2,2,6,6-tetramethylpiperidine, ketones and the 1,3-diethersof the general formula (III):

wherein R^(I) and R^(II) are the same or different and are C₁-C₁₈ alkyl,C₃-C₁₈ cycloalkyl or C₇-C₁₈ aryl radicals; R^(III) and R^(IV) are thesame or different and are C₁-C₄ alkyl radicals; or the 1,3-diethers inwhich the carbon atom in position 2 belongs to a cyclic or polycyclicstructure made up of 5, 6 or 7 carbon atoms and containing two or threeunsaturations.

Ethers of this type are described in published European patentapplications 361493 and 728769.

Preferred electron-donor compounds that can be used as external donorsinclude aromatic silicon compounds containing at least one Si—OR bond,where R is a hydrocarbon radical. A particularly preferred class ofexternal donor compounds is that of silicon compounds of formula R_(a)⁷R_(b) ⁸Si(OR⁹)_(c), where a and b are integer from 0 to 2, c is aninteger from 1 to 3 and the sum (a+b+c) is 4; R⁷, R⁸, and R⁹, are C1-C18hydrocarbon groups optionally containing heteroatoms. Particularlypreferred are the silicon compounds in which a is 1, b is 1, c is 2, atleast one of R⁷ and R⁸ is selected from branched alkyl, alkenyl,alkylene, cycloalkyl or aryl groups with 3-10 carbon atoms optionallycontaining heteroatoms and R⁹ is a C₁-C₁₀ alkyl group, in particularmethyl. Examples of such preferred silicon compounds arecyclohexyltrimethoxysilane, t-butyltrimethoxysilane,t-hexyltrimethoxysilane, cyclohexylmethyldimethoxysilane,3,3,3-trifluoropropyl-2-ethylpiperidyl-dimethoxysilane,diphenyldimethoxysilane, methyl-t-butyldimethoxysilane,dicyclopentyldimethoxysilane,2-ethylpiperidinyl-2-t-butyldimethoxysilane,(1,1,1-trifluoro-2-propyl)-methyldimethoxysilane and(1,1,1-trifluoro-2-propyl)-2-ethylpiperidinyldimethoxysilane. Moreover,are also preferred the silicon compounds in which a is 0, c is 3, R⁸ isa branched alkyl or cycloalkyl group, optionally containing heteroatoms,and R⁹ is methyl. Particularly preferred specific examples of siliconcompounds are (tert-butyl)₂Si(OCH₃)₂, (cyclohexyl)(methyl)Si(OCH₃)₂,(phenyl)₂Si(OCH₃)₂ and (cyclopentyl)₂SKOCH₃)₂.

Preferably the electron donor compound (c) is used in such an amount togive a molar ratio between the organoaluminum compound and said electrondonor compound (c) of from 0.1 to 500, more preferably from 1 to 300 andin particular from 3 to 30.

As explained above, the solid catalyst component comprises, in additionto the above electron donors, Ti, Mg and halogen. In particular, thecatalyst component comprises a titanium compound, having at least aTi-halogen bond and the above mentioned electron donor compoundssupported on a Mg halide. The magnesium halide is preferably MgCl₂ inactive form, which is widely known from the patent literature as asupport for Ziegler-Natta catalysts. Patents U.S. Pat. No. 4,298,718 andU.S. Pat. No. 4,495,338 were the first to describe the use of thesecompounds in Ziegler-Natta catalysis. It is known from these patentsthat the magnesium dihalides in active form used as support orco-support in components of catalysts for the polymerisation of olefinsare characterized by X-ray spectra in which the most intense diffractionline that appears in the spectrum of the non-active halide is diminishedin intensity and is replaced by a halo whose maximum intensity isdisplaced towards lower angles relative to that of the more intenseline.

The preferred titanium compounds are TiCl₄ and TiCl₃; furthermore, alsoTi-haloalcoholates of formula Ti(OR)n-yXy can be used, where n is thevalence of titanium, y is a number between 1 and n, X is halogen and Ris a hydrocarbon radical having from 1 to 10 carbon atoms.

The preparation of the solid catalyst component can be carried outaccording to several methods, well known and described in the art.

According to a preferred method, the solid catalyst component can beprepared by reacting a titanium compound of formula Ti(OR)n-yXy, where nis the valence of titanium and y is a number between 1 and n, preferablyTiCl₄, with a magnesium chloride deriving from an adduct of formulaMgCl₂.pROH, where p is a number between 0.1 and 6, preferably from 2 to3.5, and R is a hydrocarbon radical having 1-18 carbon atoms. The adductcan be suitably prepared in spherical form by mixing alcohol andmagnesium chloride in the presence of an inert hydrocarbon immisciblewith the adduct, operating under stirring conditions at the meltingtemperature of the adduct (100-130° C.). Then, the emulsion is quicklyquenched, thereby causing the solidification of the adduct in form ofspherical particles.

Examples of spherical adducts prepared according to this procedure aredescribed in U.S. Pat. No. 4,399,054 and U.S. Pat. No. 4,469,648. The soobtained adduct can be directly reacted with the Ti compound or it canbe previously subjected to thermally controlled dealcoholation (80-130°C.) so as to obtain an adduct in which the number of moles of alcohol isgenerally lower than 3, preferably between 0.1 and 2.5. The reactionwith the Ti compound can be carried out by suspending the adduct(dealcoholated or as such) in cold TiCl₄ (generally 0° C.); the mixtureis heated up to 80-130° C. and kept at this temperature for 0.5-2 hours.The treatment with TiCl₄ can be carried out one or more times. Theelectron donor compound(s) can be added during the treatment withTiCl_(4.)

Regardless of the preparation method used, the final amount of theelectron donor compound(s) is preferably such that the molar ratio withrespect to the MgCl₂ is from 0.01 to 1, more preferably from 0.05 to0.5.

The catalysts may be precontacted with small quantities of olefin(prepolymerisation), maintaining the catalyst in suspension in ahydrocarbon solvent, and polymerising at temperatures from ambient to60° C., thus producing a quantity of polymer from 0.5 to 3 times theweight of the catalyst. The operation can also take place in liquidmonomer, producing, in this case, a quantity of polymer 1000 times theweight of the catalyst.

By using the above mentioned catalysts, the polyolefin compositions areobtained in spheroidal particle form, the particles having an averagediameter from about 250 to 7,000 μm, a flowability of less than 30seconds and a bulk density (compacted) greater than 0.4 g/ml.

The polymerisation stages may occur in liquid phase, in gas phase orliquid-gas phase. Preferably, the polymerisation of the polymercomponent 1) is carried out in liquid monomer (e.g. using liquidpropylene as diluent), while the copolymerisation stages of theelastomeric copolymer component 2) is carried out in gas phase.Alternatively, all the sequential polymerisation stages can be carriedout in gas phase.

The reaction temperature in the polymerisation stage for the preparationof the polymer component 1) and in the preparation of the elastomericcopolymer component 2) may be the same or different, and is preferablyfrom 40 to 100° C.; more preferably, the reaction temperature rangesfrom 50 to 80° C. in the preparation of polymer component 1), and from70 to 100° C. for the preparation of polymer component 2).

The pressure of the polymerisation stage to prepare polymer component1), if carried out in liquid monomer, is the one which competes with thevapor pressure of the liquid propylene at the operating temperatureused, and it may be modified by the vapor pressure of the small quantityof inert diluent used to feed the catalyst mixture, by the overpressureof optional monomers and by the hydrogen used as molecular weightregulator.

The polymerisation pressure preferably ranges from 33 to 43 bar, if donein liquid phase, and from 5 to 30 bar if done in gas phase. Theresidence times relative to the stages depend on the desired ratiobetween polymer components 1) and 2), and can usually range from 15minutes to 8 hours. Conventional molecular weight regulators known inthe art, such as chain transfer agents (e.g. hydrogen or ZnEt₂), may beused.

The compositions of the present invention can also be obtained bypreparing separately the said components 1) and 2), by operating withthe same catalysts and substantially under the same polymerizationconditions as previously explained (except that a wholly sequentialpolymerization process will not be carried out, but the said componentswill be prepared in separate polymerization steps) and then mechanicallyblending said components in the molten or softened state. Conventionalmixing apparatuses, like screw extruders, in particular twin screwextruders, can be used.

The compositions of the present invention can also contain additivescommonly employed in the art, such as antioxidants, light stabilizers,heat stabilizers, nucleating agents, colorants and fillers.

In particular, the addition of nucleating agents brings about aconsiderable improvement in important physical-mechanical properties,such as flexural modulus, Heat Distortion Temperature (HDT), tensilestrength at yield and transparency.

Typical examples of nucleating agents are the Na benzoate, talc and the1,3- and 2,4-dibenzylidenesorbitols.

The nucleating agents are preferably added to the compositions of thepresent invention in quantities ranging from 0.01 to 2% by weight, morepreferably from 0.05 to 1% by weight with respect to the total weight.

The addition of inorganic fillers, such as talc, calcium carbonate andmineral fibers, also brings about an improvement to some mechanicalproperties, such as flexural modulus and HDT.

The particulars are given in the following examples, which are given toillustrate, without limiting, the present invention.

EXAMPLE 1

In a plant operating continuously according to the mixed liquid-gaspolymerization technique, runs were carried out under the conditionsspecified in Table 1.

The polymerization was carried out in the presence of a catalyst systemin a series of two reactors equipped with devices to transfer theproduct from one reactor to the one immediately next to it.

Preparation of the Solid Catalyst Component

The Ziegler-Natta catalyst was prepared according to the Example 5,lines 48-55 of the European Patent EP728769. Triethylaluminium (TEAL)was used as co-catalyst and dicyclopentyldimethoxysilane as externaldonor, with the weight ratios indicated in Table 1.

Catalyst System and Prepolymerization Treatment

The solid catalyst component described above was contacted at 12° C. for24 minutes with aluminium triethyl (TEAL) anddicyclopentyldimethoxysilane (DCPMS) as outside-electron-donorcomponent. The weight ratio between TEAL and the solid catalystcomponent and the weight ratio between TEAL and DCPMS are specified inTable 1.

The catalyst system is then subjected to prepolymerization bymaintaining it in suspension in liquid propylene at 20° C. for about 5minutes before introducing it into the first polymerization reactor.

Polymerization

The polymerisation run is conducted in continuous in a series of tworeactors equipped with devices to transfer the product from one reactorto the one immediately next to it. The first reactor is a liquid phasereactor, and the second reactor is a fluid bed gas phase reactor.

Polymer component 1) is prepared in the first reactor, while polymercomponent 2) is prepared in the second reactor.

Temperature and pressure are maintained constant throughout the courseof the reaction.

Hydrogen is used as molecular weight regulator.

The gas phase (propylene, ethylene and hydrogen) is continuouslyanalysed via gas-chromatography.

At the end of the run the powder is discharged and dried under anitrogen flow.

The data relating to Xylenesolubles and comonomer content in the finalpolymer compositions reported in table 1 and 2 are obtained frommeasurements carried out on the so obtained polymers, stabilized whennecessary.

Then the polymer particles are introduced in an extruder, wherein theyare mixed with 1500 ppm of Irganox B 215 (made of 1 part of Irganox 1010and 2 parts of Irgafos 168) and 500 ppm of Ca stearate. The previouslysaid Irganox 1010 is pentaerytrityl tetrakis3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoate, while Irgafos 168 istris(2,4-di-tert-butylphenyl)phosphite, both marketed by Ciba-Geigy. Thepolymer particles are extruded under nitrogen atmosphere in a twin screwextruder, at a rotation speed of 250 rpm and a melt temperature of200-250° C.

The data relating to the physical-mechanical properties of the finalpolymer compositions reported in table 2 are obtained from measurementscarried out on the so extruded polymers.

The data shown in the tables are obtained by using the following testmethods.

-   -   Molar ratios of the feed gases    -   Determined by gas-chromatography.    -   Ethylene and 1-butene content of the polymers    -   Determined by I.R. spectroscopy    -   Melt Flow Rate (MFR)    -   Determined according to ASTM D 1238, condition L (MFR“L” at 230°        C., 2.16 Kg).    -   Xylene soluble and insoluble fractions    -   Determined as follows.    -   2.5 g of polymer and 250 ml of Xylene are introduced in a glass        flask equipped with a refrigerator and a magnetical stirrer. The        temperature is raised in 30 minutes up to the boiling point of        the solvent. The so obtained clear solution is then kept under        reflux and stirring for further 30 minutes. The closed flask is        then kept for 10-15 minutes at 100° C. and in thermostatic water        bath at 25° C. for 30 minutes as well. The so formed solid is        filtered on quick filtering paper. 100 ml of the filtered liquid        is poured in a previously weighed aluminum container which is        heated on a heating plate under nitrogen flow, to remove the        solvent by evaporation. The container is then kept in an oven at        80° C. under vacuum until constant weight is obtained. The        weight percentage of polymer soluble in Xylene at room        temperature is then calculated.    -   Intrinsic Viscosity (I.V.)    -   Determined in tetrahydronaphthalene at 135° C.    -   Thermal properties (DSC):    -   The melting temperature (Tm) of the matrix component (1) is        measured on the polymer composition before the addition of        nucleating agents that can raise the melting temperature peak.        Differential scanning calorimetry (DSC) is used according to ISO        11357 with samples of 5-7 mg weight; heating and cooling rates        20° C./min, in a temperature operating range from −5° C. to 200°        C.    -   Flexural Modulus    -   Determined according to ISO 178.    -   Izod impact strength (notched)    -   Determined according to ISO180/1A.    -   Preparation of the plaque specimens    -   Plaques for D/B measurement, having dimensions of 127×127×1.5 mm        were prepared as follows.    -   The injection press was a Negri Bossi™ type (NB 90) with a        clamping force of 90 tons. The mould was a rectangular plaque        (127×127×1.5 mm)    -   The main process parameters are reported below:    -   Back pressure (bar): 20    -   Injection time (s): 3    -   Maximum Injection pressure (MPa): 14    -   Hydraulic injection pressure (MPa): 6-3    -   First holding hydraulic pressure (MPa): 4±2    -   First holding time (s): 3    -   Second holding hydraulic pressure (MPa): 3±2    -   Second holding time (s): 7    -   Cooling time (s): 20    -   Mould temperature (° C.): 60    -   The melt temperature was between 220 and 280° C.    -   Plaques for haze measurement, 1 mm thick, were prepared by        injection moulding with injection time of 1 second, temperature        of 230° C., mould temperature of 40° C.    -   The injection press was a Battenfeld™ type BA 500CD with a        clamping force of 50 tons. The insert mould led to the moulding        of two plaques (55×60×1 mm each).    -   Ductile/Brittle transition temperature (D/B)    -   Determined according to the following method. The bi-axial        impact resistance was determined through impact with an        automatic, computerised striking hammer.    -   The circular test specimens were obtained from plaques, prepared        as described above, by cutting with circular hand punch (38 mm        diameter). They were conditioned for at least 12 hours at 23° C.        and 50 RH and then placed in a thermostatic bath at testing        temperature for 1 hour.    -   The force-time curve was detected during impact of a striking        hammer (5.3 kg, hemispheric punch with a 1.27 cm diameter) on        the circular specimen resting on a ring support. The machine        used was a CEAST 6758/000 type model No. 2.    -   D/B transition temperature means the temperature at which 50% of        the samples undergoes fragile break when submitted to the said        impact test.    -   Haze on plaque    -   Determined according to the following method. The plaques,        prepared as described above, were conditioned for 12 to 48 hours        at relative humidity of 50±5% and temperature of 23±1° C.    -   The instrument used for the test was a Gardner photometer with        Haze-meter UX-10 equipped with a G.E. 1209 lamp and filter C.        The instrument calibration was made by carrying out a        measurement in the absence of the sample (0% Haze) and a        measurement with intercepted light beam (100% Haze).    -   The measurement and computation principle are given in the norm        ASTM-D1003.    -   The haze measurement was carried out on five plaques.    -   Gloss on plaque    -   10 rectangular specimens (55×60×1 mm) for each polymer to be        tested were prepared by injection molding using an injection        press Battenfeld BA500CD operated under the following        conditions:    -   Screw speed: 120 rpm    -   Back pressure: 10 bar    -   Mould temperature: 40° C.    -   Melt temperature: 260° C.    -   Injection time: 3 sec    -   First holding time: 5 sec    -   Second holding time: 5 sec    -   Cooling time (after second holding): 10 sec    -   The value of the injection pressure should be sufficient to        completely fill the mould in the above mentioned indicated time        span.    -   By a glossmeter the fraction of luminous flow reflected by the        examined specimens surface was measured, under an incident angle        of 60°. The value reported in table 2 corresponds to the mean        gloss value over 10 specimens for each tested polymer.    -   The glossmeter used was a photometer Zehntner model ZGM 1020 or        1022 set with an incident angle of 60°. The measurement        principle is given in the Norm ASTM D2457.    -   The apparatus calibration is done with a sample having a known        gloss value.    -   Preparation of the cast film specimens    -   Films with a thickness of 50 μm were prepared by extruding each        polymer composition in a single screw Collin extruder        (length/diameter ratio of screw: 30) at a film drawing speed of        7 m/min and a melt temperature of 210-250° C.    -   Haze on film    -   Determined on 50 μm thick films of the test composition,        prepared as described above. The measurement was carried out on        a 50×50 mm portion cut from the central zone of the film.    -   The instrument used for the test was a Gardner photometer with        Haze-meter UX-10 equipped with a G.E. 1209 lamp and filter C.        The instrument calibration was made by carrying out a        measurement in the absence of the sample (0% Haze) and a        measurement with intercepted light beam (100% Haze).    -   Gloss on film    -   Determined on the same specimens as for the Haze.    -   The instrument used for the test was a model 1020 Zehntner        photometer for incident measurements. The calibration was made        by carrying out a measurement at incidence angle of 60° on black        glass having a standard Gloss of 96.2% and a measurement at an        incidence angle of 45° on black glass having a standard Gloss of        55.4%.    -   Fish eyes:    -   Determined on a 50 μm-thick film specimen prepared as described        above. The film is then inspected by means of an optical device        (Matrix or Line CCD cameras). Film defects are counted in        accordance to their dimension.

COMPARATIVE EXAMPLE 1c

The comparative example (properties reported in table 2) is anheterophasic composition having a random propylene copolymer matrix withan ethylene content of 2.8 wt % and an ethylene-butene elastomeric(rubber) component.

The examples demonstrates that heterophasic compositions not having allthe features according to the present invention (particularly MFR, Tmand XStot/XSm) do not provide the valuable balance of properties of theinvention.

TABLE 1 Polymerization Process EXAMPLE 1 TEAL/solid catalyst componentweight ratio 6 TEAL/DCPMS molar ratio 10 liquid phase reactor: propylenehomopolymer matrix Polymerisation temperature, ° C. 70 Pressure, Mpa3.92 Residence time, min 72 H₂ feed mol ppm 4900 MFR “L” g/10 min 6.7Xylene soluble fraction wt % 1.5 Split wt % 78 gas phasereactor—ethylene-butene-1 copolymer rubber Polymerisation temperature, °C. 85 Pressure, bar 15 Residence time, min 11 H₂/C₂ ⁻ mol ratio 0.25 C₄⁻/(C₄ ⁻ + C₂ ⁻) Mol ratio 0.45 Split wt % 22 Butene-1 in the rubber wt %25 Xylene soluble fraction wt % 15.6 Notes: H₂ feed = calculated withrespect to the molar flow of propylene; C₂ ⁻ = ethylene; C₃ ⁻ =propylene; C₄ ⁻ = butene-1

TABLE 2 Examples 1 lc Matrix properties MFR g/10 min 6.7 1.5 XSm % 1.54.4 Tm ° C. 162.5 144.9 Comonomer content (C₂) % 0 2.8 Split wt % 78 80Composition MFR “L” g/10 min 7.2 1.8 XStot wt % 15.6 14.2 XStot/XSm 10.33.2 XSIVtot dl/g 1.2 1.42 Ethylene content wt % 16.5 18.3 Butene-1content wt % 5.6 4.1 Properties Flexural modulus MPa 1150 870 Izodimpact resistance at 23° C. kJ/m² 7.6 58.7 D/B transition temperature °C. −28 −22.7 Haze on plaque (1 mm) % 46.3 14.3 Gloss on plaque (1 mm) at60° % 91.8 — Characterization on cast film 50 μ Haze on cast film (50μm) % 3.1 9 Gloss on cast film (50 μm) at 45° % 79 — Fish eyes >1.5 mm(n°/m²) 0 0 Fish eyes 0.7-1.5 mm (n°/m²) 3 8 Fish eyes 0.5-0 7 mm(n°/m²) 6 26 Fish eyes > 0.1 mm (n°/m²) 196 1450

1. Polyolefin compositions comprising, in percent by weight referred tothe sum of component 1) and 2): 1) 75-85 wt % of a propylene homopolymeror copolymer of propylene with at least one of ethylene and C₄-C₁₀α-olefin(s), the homopolymer or copolymer having a melting temperatureequal to or higher than 150° C., and 2) 15-25% of a copolymer ofethylene with at least one C₄-C₁₀ α-olefin containing from 20 to 30% ofsaid C₄-C₁₀ α-olefin(s); said composition having a value of MFR at 230°C., 2.16 kg of from 5 to 10 g/10 min, a total content of ethylene offrom 10 to 20%, a total content of C₄-C₁₀ α-olefin(s) of from 2 to 8%, aratio XStot/XSm of the total fraction soluble in Xylene at roomtemperature to the fraction soluble in Xylene at room temperature of thecomponent (1) of from 5 to 15, and a value XSIVtot of the intrinsicviscosity of the total fraction soluble in Xylene at room temperature ofat most 1.5 dl/g.
 2. The polyolefin compositions of claim 1, wherein thefraction soluble in Xylene at room temperature of component (1) is atmost 2 wt %.
 3. The polyolefin compositions of claim 1, wherein thematrix component (1) is a copolymer of propylene and the amount of unitsderived from the at least one of ethylene and C₄-C₁₀ α-olefin(s) is atmost 1.5 wt % of the component (1).
 4. A process for producing thepolyolefin compositions of claim 1 comprising polymerizing olefins in atleast two sequential polymerization stages with each subsequentpolymerization stage being conducted in the presence of the polymericmaterial formed in the immediately preceding polymerization stage.
 5. Afilm comprising the polyolefin compositions according to claim
 1. 6. Thefilm of claim 5 wherein the film is a cast film.
 7. Injection moldedarticles comprising the polyolefin compositions according to claim 1.